The existence of multiple nuts in which the kernel, i.e., the part which can be used for consumption, is covered with a shell with a degree of hardness which varies considerably among nuts is generally known. Even within the same nut, there are occasionally different varieties nuts in which the degree of hardness of a shell is likewise variable. Such is the case of almonds, in which the degree of hardness of the shell varies considerably from one variety to another. Therefore, the shelling process must necessarily be designed according to the structural features of the shell.
The existence of machines which have specifically been designed to automatically shell the almonds or other nuts with similar characteristics is already known on the market. For example, Spanish Utility Model number U-200601131 owned by the same applicant as the present invention and incorporated herein by reference describes a shelling-separating machine for almonds in which the shelling element consists of a rotary shaft provided with multiple filiform elements which, like fingers longitudinally provided with a certain curvature, project radially from said rotary shaft, starting from aligned positions according to different generatrices of the rotary shaft. These elements act directly on the shell of the nut and cause it to break, in order to extract the kernel through an outlet hopper provided for such purpose, and to expel the sticks and shells through an outlet mouth located at the end opposite to the product access end.
However, experience has demonstrated that in practice, soft-shelled almonds are usually mixed with a certain percentage of hard-shelled almonds, which is about 10% to 20%. These hard-shelled almonds evidently require a different treatment, as it is impossible to break their shell to extract the kernel with the use of the same machine as is used for the softer-shelled almonds.
Therefore, although the machine described in the mentioned prior utility model perfectly fulfills the mission for which it was developed, it has been verified in practice that the modification of some of the structural features for the purpose of providing continuous feed means, together with retaining the hard-shelled almonds (i.e., the non-shelled nuts) at the outlet of the machine, all of this being controlled by measuring and controlling a certain functional parameter, allows carrying out a selection of soft-shelled almonds among hard-shelled almonds, in order to extract the kernel from the first type of almonds and expel the second type of almonds, when certain levels of the control parameter are exceeded, the expelling action of which can be manually or automatically controlled.